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> Quick question about AA pistons..., Which way does the arrow point?
BMXerror
post May 3 2008, 09:12 PM
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Well, anyone who's used them? Does the arrow point up or down?
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SLITS
post May 3 2008, 09:53 PM
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I would hazard a guess, but I don't want to be wrong and ruin your engine.
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McMark
post May 3 2008, 09:59 PM
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The piston industry standard is to make a mark that points to the flywheel. Are these the pistons with the valve relief pocket? If so, the pocket does DOWN, regardless of anything else.


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BMXerror
post May 3 2008, 10:05 PM
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No, they're basically 1.7 Euro stockers, but the arrow points up or down? WTF?
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SLITS
post May 3 2008, 10:13 PM
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Are there any other markings on the piston crowns?
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brer
post May 4 2008, 11:34 AM
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pics?
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Allan
post May 4 2008, 11:55 AM
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Look inside the pistons and see if there is a little crank looking mark. Kinda looks like a zig-zag with a straight line at one end.
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BMXerror
post May 4 2008, 12:22 PM
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QUOTE(brer @ May 4 2008, 10:34 AM) *

pics?

Only the mystery arrow and a number (89.95). I'm guessing it's either weight or bore. No marks on the inside either except an AA logo cast into one side. BTW, what's the difference? Is the wrist pin hole offset or something? I'm emailing AA today, but I probably won't hear from them 'till tomorrow.
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BMXerror
post May 4 2008, 12:26 PM
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Pic.
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brer
post May 4 2008, 09:18 PM
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only AA can help you me thinks.

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tod914
post May 5 2008, 01:05 AM
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Is it possible the arrows where removed and put on a 6 cyl set? (IMG:style_emoticons/default/WTF.gif)
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hot_shoe914
post Sep 22 2011, 03:08 PM
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QUOTE(McMark @ May 3 2008, 10:59 PM) *

The piston industry standard is to make a mark that points to the flywheel. Are these the pistons with the valve relief pocket? If so, the pocket does DOWN, regardless of anything else.

Bumping this for someone.
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hot_shoe914
post Sep 22 2011, 03:24 PM
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Here is my question. If the pushrods are on the bottom, the rockers in the middle, then the valves are up top, shouldn't the valve relief need to be up top also?
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draganc
post Sep 22 2011, 08:34 PM
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QUOTE(McMark @ May 3 2008, 07:59 PM) *

...The piston industry standard is to make a mark that points to the flywheel...


Mark, can you elaborate on your comment? I was told that the arrow always points to the exhaust.

How would the arrow/mark point to the fly-wheel on our engines?

Not to be a smart-ass, just curious.


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Dr Evil
post Sep 22 2011, 10:02 PM
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The arrows above point up and down. That is not the norm. The norm is fore and aft. The flywheel is on one of those points and the arrow fore or aft woudl point to the fly wheel.
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biggy72
post Sep 23 2011, 12:17 AM
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I know the arrow always points toward the exhaust on Stihl products. That's what I have the most experience with. It may or may not be correct in this instance though.
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draganc
post Sep 23 2011, 03:47 PM
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QUOTE(Dr Evil @ Sep 22 2011, 08:02 PM) *

The arrows above point up and down. That is not the norm. The norm is fore and aft. The flywheel is on one of those points and the arrow fore or aft woudl point to the fly wheel.


doc, but wouldn't that flip the pistion by 180deg from "left" to "right" side. i.e. if my left bank points to the flywheel, i would have to flip the pisiton by 180deg on the right side in order to point to the flywheel.

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Dr Evil
post Sep 23 2011, 04:12 PM
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Yes, one would have to flip the pistons to point all in the same direction. If this conflicts with the piston pocket orientation (if there are any) then you have 4 of the same side. Not good.
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Series9
post Sep 23 2011, 06:22 PM
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I'm looking forward to this answer.

I've seen arrows both flywheel and nose, but never up or down.
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r_towle
post Sep 23 2011, 06:42 PM
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measure the wrist pin placement to see if it is centered in the diameter of the piston.
If it is offset (somewhere around 8mm) that would be the bottom of the piston on a stock motor....and the top in a race motor...lol

If they are offset, you want the rod closer to the bottom of the motor...I hope that makes sense.

Makes it quieter with less piston slap when it reverses direction.

Early 911 had this...then it went away..then it came back again.
beetle and 356 and type 4 have the offset pins.

Rich
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